[PATCH v6 1/2] perf pmu intel: Generalize SNC cpumask adjustment for multiple platforms

[Chun-Tse Shao <ctshao@google.com>]

Prepare for supporting more Intel platforms with sub-NUMA clustering by
generalizing the GNR specific logic.

Signed-off-by: Chun-Tse Shao <ctshao@google.com>
---
v6:
  Make string literal.
  Add SPR into SNC2.

v5: lore.kernel.org/20260407203918.3178481-1-ctshao@google.com/
  Split patch.

v4: lore.kernel.org/20260402205300.1953706-1-ctshao@google.com
  Rebase.

v3: lore.kernel.org/20260212223942.3832857-1-ctshao@google.com
  Fix a typo.

v2: lore.kernel.org/20260205232220.1980168-1-ctshao@google.com
  Split EMR and GNR in the SNC2 IMC cpu map.

v1: lore.kernel.org/20260108184430.1210223-1-ctshao@google.com

 tools/perf/arch/x86/util/pmu.c | 46 +++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/tools/perf/arch/x86/util/pmu.c b/tools/perf/arch/x86/util/pmu.c
index 7c9d238922a6..b8fab260c423 100644
--- a/tools/perf/arch/x86/util/pmu.c
+++ b/tools/perf/arch/x86/util/pmu.c
@@ -22,20 +22,30 @@
 #include "util/env.h"
 #include "util/header.h"

-static bool x86__is_intel_graniterapids(void)
+#define GENUINE_INTEL_GNR "GenuineIntel-6-A[DE]"
+
+static bool x86__is_snc_supported(void)
 {
-	static bool checked_if_graniterapids;
-	static bool is_graniterapids;
+	static bool checked_if_snc_supported;
+	static bool is_supported;
+
+	if (!checked_if_snc_supported) {

-	if (!checked_if_graniterapids) {
-		const char *graniterapids_cpuid = "GenuineIntel-6-A[DE]";
+		/* Graniterapids supports SNC configuration. */
+		static const char *const supported_cpuids[] = {
+			GENUINE_INTEL_GNR, /* Graniterapids */
+		};
 		char *cpuid = get_cpuid_str((struct perf_cpu){0});

-		is_graniterapids = cpuid && strcmp_cpuid_str(graniterapids_cpuid, cpuid) == 0;
+		for (size_t i = 0; i < ARRAY_SIZE(supported_cpuids); i++) {
+			is_supported = cpuid && strcmp_cpuid_str(supported_cpuids[i], cpuid) == 0;
+			if (is_supported)
+				break;
+		}
 		free(cpuid);
-		checked_if_graniterapids = true;
+		checked_if_snc_supported = true;
 	}
-	return is_graniterapids;
+	return is_supported;
 }

 static struct perf_cpu_map *read_sysfs_cpu_map(const char *sysfs_path)
@@ -132,8 +142,8 @@ static int uncore_imc_snc(struct perf_pmu *pmu)
 	// Compute the IMC SNC using lookup tables.
 	unsigned int imc_num;
 	int snc_nodes = snc_nodes_per_l3_cache();
-	const u8 snc2_map[] = {1, 1, 0, 0, 1, 1, 0, 0};
-	const u8 snc3_map[] = {1, 1, 0, 0, 2, 2, 1, 1, 0, 0, 2, 2};
+	const u8 snc2_map[] = {1, 1, 0, 0};
+	const u8 snc3_map[] = {1, 1, 0, 0, 2, 2};
 	const u8 *snc_map;
 	size_t snc_map_len;

@@ -156,11 +166,12 @@ static int uncore_imc_snc(struct perf_pmu *pmu)
 		pr_warning("Unexpected: unable to compute IMC number '%s'\n", pmu->name);
 		return 0;
 	}
-	if (imc_num >= snc_map_len) {
+	if (imc_num >= snc_map_len * perf_cpu_map__nr(pmu->cpus)) {
 		pr_warning("Unexpected IMC %d for SNC%d mapping\n", imc_num, snc_nodes);
 		return 0;
 	}
-	return snc_map[imc_num];
+
+	return snc_map[imc_num % snc_map_len];
 }

 static int uncore_cha_imc_compute_cpu_adjust(int pmu_snc)
@@ -200,7 +211,7 @@ static int uncore_cha_imc_compute_cpu_adjust(int pmu_snc)
 	return cpu_adjust[pmu_snc];
 }

-static void gnr_uncore_cha_imc_adjust_cpumask_for_snc(struct perf_pmu *pmu, bool cha)
+static void uncore_cha_imc_adjust_cpumask_for_snc(struct perf_pmu *pmu, bool cha)
 {
 	// With sub-NUMA clustering (SNC) there is a NUMA node per SNC in the
 	// topology. For example, a two socket graniterapids machine may be set
@@ -300,11 +311,12 @@ void perf_pmu__arch_init(struct perf_pmu *pmu)
 				pmu->mem_events = perf_mem_events_intel_aux;
 			else
 				pmu->mem_events = perf_mem_events_intel;
-		} else if (x86__is_intel_graniterapids()) {
+		} else if (x86__is_snc_supported()) {
 			if (strstarts(pmu->name, "uncore_cha_"))
-				gnr_uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/true);
-			else if (strstarts(pmu->name, "uncore_imc_"))
-				gnr_uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/false);
+				uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/true);
+			else if (strstarts(pmu->name, "uncore_imc_") &&
+				 !strstarts(pmu->name, "uncore_imc_free_running"))
+				uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/false);
 		}
 	}
 }
--
2.54.0.669.g59709faab0-goog